A brief discussion on the issues to be considered in the electrical design and commissioning of dry quenching coke elevators

Thread Content

Looking at the dry quenching projects that have been implemented one after another, although the commissioning of elevators has become more mature and refined, there are still certain issues to be addressed in terms of their actual operation. Analyzing the problems that arise with these elevators, it can be seen that most of them are caused by defects in the initial design of the elevators as well as insufficient subsequent commissioning. So, what issues should be taken into account during the design and commissioning process of elevators in order to ensure their smoother operation and greater safety and reliability? !SO8O 1: Improvements are needed in the design. 54{q.I@n 1.1: Generally speaking, the design of elevators is based on scientific principles and logic, but various problems often arise during actual use. For example, the sensing elements on elevators generally share a DC power supply (commonly referred to as low-voltage power); these elements are not isolated from one another. If one of them becomes grounded or short-circuited, it can bring the entire DC power supply system to a halt or cause failures in certain modules. Such faults are difficult to detect promptly, as it’s hard to determine which element is at fault. Therefore, in terms of design, it might be advisable to provide separate power supplies for all the sensing elements on site, ensuring that each element has its own independent power supply, so that a failure in one element will not cause the entire system to fail. %d1draL 1.2 Choosing an appropriate control system: |S&5es-yW There are various PLC control systems from abroad available in the domestic market, and their functionality and reliability are recognized by many people; however, not all of them are suitable for use in controlling elevators. For example, PLC controllers from certain foreign brands, despite having extensive functions and fast processing capabilities, lack the ability to suppress interference compared to other products. Moreover, their communication and data transmission use different protocols, and the communication network must be kept at a distance of more than 2 meters from sources of interference. Such installation requirements are difficult to meet in elevators, which further hinders their efficient operation over the long term. 9xFO]Y" 1.3 Choose power transmission cables with high performance indicators: %T!J$a)qf Since bus control is used between the local and remote stations of the elevator, data on-site is transmitted to the main station via the data bus. However, bus cables have poor interference resistance; especially in the presence of high-power inductive loads, they are easily disturbed by factors such as current and high-frequency radio waves, which can lead to data loss. This prevents the controller from performing calculations, resulting in malfunctions in the operating equipment. Secondly, since the power transmission cable of the elevator has to pass through a moving cable cart, it is necessary that the power cable possess good flexibility. To prevent interference from the power cable with the bus system and to accommodate local annual temperature variations, it is advisable to use high-temperature resistant, flexible, shielded cables for this purpose. 06 i;T~Y II: Hoist commissioning. Hoist commissioning is a very important process in the dry quenching of coke projects; whether the commissioning is thorough determines not only the hoist’s production capacity but also the safe and stable operation of the dry quenching process. For a special type of lifting equipment that requires fully automated operation throughout its lifecycle in order to maintain efficient performance, the commissioning of such a lift is of great significance for its future operation. c0_E_~ 2.1: First, it is necessary to establish the operating speed curve of the elevator. The speed curve is used to calculate the time required for the elevator to complete one cycle of operation, and it is also an important guarantee for meeting production requirements. To ensure that the operating cycle of the elevator meets production requirements, the speed curve must not only be smooth, but the elevator should also operate as slowly as possible while still meeting the time constraints, in order to prevent it from getting out of control; high-speed operation of the elevator is strictly prohibited below the standby position. tnz+bX26 2.2: The speed is specified as =WG=C1Z. For setting the lifting and operating speeds of the elevator, a reasonable distribution is necessary; since the effective distance at which a high speed can be maintained over the entire speed range fY,|o3# is not very long, priority should be given to ensuring the safe operation of the elevator }tG3tz0%fX. Therefore, whether it is in lifting mode or in reciprocating motion, its speed should be kept below 85% of the rated speed @F~LW6K. The boost speed is generally around 45 Hz, while the operating speed is usually below 40 Hz. And At6qtoPRA ensures that the inverter has sufficient acceleration and deceleration time, so that the elevator maintains smooth and stable operation when its speed changes. uH@FU60 2.3: Installation of detection elements. The detection elements in key positions must be installed in a proper and reliable manner. The sensing element at the opening of the hook serves both to return it to its initial starting position and to adjust the degree of opening of the hook. The installation of the upper limit detection element of the lifting tower must ensure a sufficient safety distance from the upper limit; the alignment signals at the lifting tower and the cooling tower must remain within the allowable design errors. For the lower limit of the cooling tower, it is sufficient for the bottom door of the coke tank to open at an angle of 45 degrees – if this angle is too small, the hook may come loose, while if it is too large, the bottom door of the coke tank cannot open fully. +nL+ N 2.4: Debugging of protection components. The elevator is equipped with various safety protection components, such as weight limit switches, load limiters, wire rope extension detectors, anemometers, anchoring switches, and so on. These protection components play a very important role in ensuring the safe operation of the elevator. The load limiter not only detects overloading and uneven loading of the coke tank, but also can issue an alarm when the ropes need to be loosened. It is important to note, however, that when calibrating the coke tank, the calibration values must be accurate; otherwise, the load limiter will be unable to provide protection. For detecting the elongation of steel wire ropes, rotary limiters are generally used. If a rotary limiter with high gear ratio accuracy cannot be selected, its reliability is low; the smaller the gear ratio, the higher the accuracy. The gear ratio of rotary limiters in elevators in China is usually below 1:25. The weight hammer limit is the final level of protection for the elevator during lifting, and its significance and role are extremely important. When adjusting the weight limiter, one cannot rely solely on simulation tests; actual experiments are necessary to achieve the power-off effect. These protection elements must be specified in the power conditions during programming, or applied as pulse blocking conditions in a strict manner, and repeated experiments are required. "*z_O 2.5: Hoist interlock debugging. The coordinated debugging of the hoist is crucial for achieving unmanned operation in automated processes; the quality of this debugging determines the production capacity of dry quenching of coke. Therefore, the coordinated debugging of the hoist is extremely important. &a, OfSz Since most domestic dry quenching projects adopt a design in which the main system and the elevator system operate independently, the main system can only rely on the elevator to obtain information regarding it; this communication usually takes place through digital signal connections. To enable automated operation, the main system must receive accurate signals from the elevator, so that it can issue the correct commands; otherwise, automatic operation is not possible. Based on the information provided by the elevator, the host system generally divides the entire operation process into 7 action phases; each phase represents the current state of the elevator’s operation. For every command sent by the system, the elevator must carry out one specific action, and it simultaneously sends back information regarding its current action status and position to the host system. The host system uses this information to determine whether the elevator is acting correctly and whether it is time to issue the next command. The 7-stage sequence is as follows: the standby position descends until the hook opens; from the position where the hook is open, it moves towards startup; it moves towards the lifting tower; the cooling tower descends; the cooling tower rises; it moves again from the position of the cooling tower; and the lifting tower descends back to the standby position. The elevator’s ability to determine direction and adjust speed can only be achieved through its own system programs; it provides the main system with information regarding its operating status and position. During debugging, repeated adjustments are necessary, and each phase of operation also requires repeated testing to ensure that there are no incorrect commands or actions. For signals coming from outside the system, such as APS signals, lifting command signals, or requests to stop the elevator when a locomotive is in a standby position, the elevator must have the capability to recognize these signals. It cannot simply execute only the commands issued by the system; it is essential to assess external signals as well, as this is a crucial factor in ensuring the safe operation of the elevator. ~utJB 'gr 2.6: Fault alarm debugging. Regarding the fault alarm information of the elevator, the main system must be able to track it throughout the entire process. The elevator system must also provide the main system with detailed alarm information that is clear and accurate, without any omissions. Fault information cannot be suppressed, and no other system besides the elevator itself may reset faults. During testing, it is possible to repeatedly simulate the elevator’s state when a fault occurs, in order to prevent the elevator from getting out of control